According to MyScreenEvent.com the NKOTBSB show in London on April 29, 2012 will be broadcasted LIVE at several local movie theaters around Europe. The below quoted article is probably an public announcement to the cinemas.

ONE STAGE – ONCE IN A LIFETIME
For once, all the rumors are actually true! Record breaking hits like “The Right Stuff” “Step By Step” “Quit Playing Games With My Heart” “Everybody (Backstreet’s Back)”

New Kids On The Block join forces with Backstreet Boys to form NKOTBSB. TWO OF THE BIGGEST BANDS IN THE WORLD – NKOTBSB will exclusively be on your local cinema live from the O2 Arena, London. All the classics and new songs will be performed!

Read full announcement on MyScreenEvent.com.